Pavel gives you all the basics, and it could be reasonably argued that you don't need anything else. However, I think Martone's work is important for several reasons.
First of all, despite the fact that Pavel's name is almost synonymous with kettlebells in the US, he's marketing various fitness products, many of which have nothing to do with kettlebells. However, Martone seems to specialize in kettlebells.
Secondly, while Pavel's instruction is very high-energy and motivational, Jeff's teaching style is more casual and informational. He provides nuances that Pavel doesn't even mention.
Also, Jeff Martone mixes it up, giving little variations to keep things interesting. With Pavel, you can design a perfect workout for life. With Martone, you can easily make every workout a little different, which keeps it interesting. Don't let me give you the impression that Jeff gives you a bunch of new moves and complicates things. Rather, he explains minor variations in the same exercises, and I think that makes them more fun and less repetitive.
I haven't yet seen any of his DVDs, but the video clips I watched were great, and his teaching style was excellent. It could be that the videos were of him teaching other personal trainers and not end-users, but I really felt like I was getting all the in-depth info.